dashboard: browser notifications for operator-bound events

three signals fire OS notifications:
- new approval lands in the queue (per id, via /api/state delta)
- new ask_operator question queued (per id)
- broker message sent to operator (live via SSE)

first /api/state render after page load seeds the 'seen' sets
without firing — only items that arrive while the page is open
count. controls in a row under the banner: 🔔 enable
notifications (calls requestPermission, hides on grant), 🔕 mute /
🔔 unmute toggle (localStorage-backed so operator can silence
without revoking the permission), inline status text when blocked
or unsupported.

notification tag='hyperhive' collapses rapid bursts; onclick
focuses the dashboard tab. requires secure context (HTTPS or
localhost) — on other origins the API is unavailable and the
controls hide themselves.

todo: entry dropped.

hive-c0re/assets/dashboard.css

@@ -190,6 +190,32 @@ a:hover {
   word-break: normal;
 }
 
+/* Notification controls — sit between the banner and the
+   containers section. Hidden by JS when notifications are
+   unsupported, denied, or already in the right state. */
+.notif-row {
+  display: flex;
+  gap: 0.5em;
+  align-items: center;
+  margin: 0.5em 0;
+  font-size: 0.85em;
+}
+.btn-notif {
+  font-family: inherit;
+  font-size: 0.85em;
+  background: transparent;
+  color: var(--cyan);
+  border: 1px solid var(--cyan);
+  padding: 0.2em 0.7em;
+  border-radius: 999px;
+  cursor: pointer;
+  text-shadow: 0 0 4px currentColor;
+}
+.btn-notif:hover {
+  background: rgba(137, 220, 235, 0.1);
+  box-shadow: 0 0 10px -2px currentColor;
+}
+
 .pending-state {
   color: var(--amber);
   font-size: 0.85em;